This invention relates to a method for producing a cooling member and a cooling member produced by the method.
According to the recent progress in the field of semiconductor technique, semiconductor elements of a large capacity operable at 4000V-3000A or more one triggered directly with light signal have been developed and are used practically. In such a semiconductor element, since several kW of heat is generated in a small area of the electrodes of the semiconductor element, a cooling device of an extremely large capability is required.
In order to satisfy such a requirement, heretofore has been proposed a heat sink made of a highly heat-conductive metal such as copper or aluminum, through which a circulation passage of a liquid coolant is provided in a zigzag form. In a typical application, a required number of the heat sinks are placed between semiconductor elements such as diodes, thyristors, gate turn off (GTO) thyristors and the like, respectively, and the coolant passages formed in the heat sinks are connected together through a member of coolant supplying pipes made of an electrically insulating material so as to provide a coolant circulating path. By circulating a liquid coolant such as water through the coolant circulating path by means of a coolant circulating pump provided in the path, the heat generated in the semiconductor elements is transferred to the coolant and carried outside of the semiconductor elements.
In the aforementioned heat sink, however, the thickness of the heat sink becomes comparatively thick not only because of the heat-conductive metal member through which the zigzag formed circulation passage is provided, but also because of the zigzag-formed configuration, the head loss caused when the liquid coolant flows through the circulation passage in each heat sink becomes high, thus requiring a large capacity of the pump for circulating the liquid coolant therethrough. Furthermore, the temperature of the liquid coolant becomes much different between the inlet portion and outlet portion of the coolant passage in each heat sink, which entails a difficulty of increasing the thermal stress in the semiconductor element and requiring a heat exchanger of a large capacity in the coolant circulating path.